citygisoo 0.2.1

PyQGIS utilities and cleaning workflows for CityGISOO

citygisoo

Project Developer: Alireza Adli

Table of Contents

• What Is citygisoo
• Approach and Scope
• citygisoo in Sabu
• Testing and Publication Context
• Logging
• ScrubLayer
• FieldSchemaManager
• BuildingContractAdapter
• Setting up an environment to use standalone PyQGIS - How to import qgis.core
• Name and Dedication

What Is citygisoo

citygisoo is a Python package that leverages PyQGIS functions for cleaning building-related geospatial data, with the goal of supporting automated data-cleaning pipelines.

The name citygisoo stands for Object-Oriented Geographic Information System for Cities.

The package follows an object-oriented design. Its central component is the ScrubLayer class, which consolidates key cleaning and transformation operations commonly used in city-scale workflows.

Approach and Scope

citygisoo builds on existing PyQGIS functionality and, where necessary, extends or combines these capabilities to support additional operations required for automated geospatial data cleaning.

The design principles and methodology behind this approach will be discussed in more detail in upcoming papers and reports.

citygisoo in Sabu

citygisoo is a shared library within the Sabu project.

Sabu is a sector-based carbon-emission evaluation framework built on a microservices architecture.

Each module runs as an independent service (a “jug”). Current services focus on building life-cycle assessment and city-scale geospatial cleaning and validation workflows. In addition to these services, Sabu includes shared Python libraries such as sabu-chassis, which provide reusable internal functionality.

Testing and Publication Context

citygisoo was initially tested using geospatial data from Montréal Island.

It is now being published so that it can be applied to other cities simply by installing the package via pip.

Logging

citygisoo uses the sabu-chassis logging system to provide consistent operational messages across its workflows. Layer loading, exports, schema changes, cleaning operations, and adapter runs report progress and failures through package loggers instead of ad hoc console output.

This makes citygisoo easier to use inside larger Sabu workflows while still keeping the package useful in standalone PyQGIS scripts.

ScrubLayer

ScrubLayer is the core class of the package. It wraps and orchestrates essential PyQGIS operations used in geospatial cleaning workflows and provides higher-level methods for automating multi-step tasks.

FieldSchemaManager

FieldSchemaManager manages attribute-field schema operations for PyQGIS map layers. It can work with an existing ScrubLayer instance or load a layer directly from a file path.

The class is designed for preparing layer attributes without changing feature geometries. It supports common schema-cleaning tasks such as listing fields, checking required fields, renaming fields, dropping fields, keeping only selected fields, reordering fields, exporting layers to GeoJSON, detecting null-like required values, removing incomplete features, adding ID fields, and promoting GeoJSON IDs to the feature level.

FieldSchemaManager is useful when a workflow needs the same field-preparation logic across different supported layer formats, including Shapefile and GeoJSON.

BuildingContractAdapter

BuildingContractAdapter prepares building map layers for a standardized GeoJSON building contract used by downstream workflows such as UBEM archetype assignment.

The adapter uses FieldSchemaManager to orchestrate the field-preparation workflow. It validates required source fields, exports the input layer to GeoJSON, renames source fields into the expected contract schema, keeps only required contract fields, removes features with missing required values, adds generated integer IDs, and promotes those IDs to GeoJSON feature-level IDs.

This class is intended for repeatable city-specific building-data preparation, where the input layer may use local field names but the downstream service expects a stable contract schema.

Setting up an environment to use standalone PyQGIS - How to import qgis.core

To use PyQGIS without having the QGIS application run in the background, one needs to add the python path to the environment variables. Here is how to do it on Windows:

1. Install QGIS.

2. Assign a specific name to the QGIS Python executable. This is done to access QGIS Python from command prompt without mixing with the system Python installation(s).

   a. Go to the QGIS installation directory's Python folder (for example: C:\Program Files\QGIS 3.34.1\apps\Python39).
   b. Rename the Python executable (python.exe) to a specific desired name, for example pythonqgis.exe.

3. Update environment variables.

   a. Open Environment Variables from Windows Start.
   b. Edit Path and add:

   C:\Program Files\QGIS 3.34.1\apps\Python39

   c. Create/Edit PYTHONPATH and add (separated by semicolons):

   i. C:\Program Files\QGIS 3.34.1\apps\qgis\python
   ii. C:\Program Files\QGIS 3.34.1\apps\qgis\python\plugins
   iii. C:\Program Files\QGIS 3.34.1\apps\Qt5\plugins
   iv. C:\Program Files\QGIS 3.34.1\apps\gdal\share\gdal
   v. Or all together: C:\Program Files\QGIS 3.34.1\apps\qgis\python;C:\Program Files\QGIS 3.34.1\apps\qgis\python\plugins;C:\Program Files\QGIS 3.34.1\apps\Qt5\plugins;C:\Program Files\QGIS 3.34.1\apps\gdal\share\gdal

4. Validate importing qgis.core.

   a. Open a command prompt window. b. Run pythonqgis. c. If setup is correct, there should be no import error. d. In Python, run:

   import qgis.core

citygisoo must be installed with pip in the interpreter configured above.

Name and Dedication

In Persian, gisoo refers to long hair, especially long or braided hair, and the word is most commonly used when speaking about a woman’s hair.

I began developing this project in the aftermath of the Woman, Life, Freedom movement in Iran. The movement emerged following the killing of Mahsa Jina Amini, who died in the custody of the Islamic Republic’s morality police after being arrested for allegedly violating the state’s compulsory hijab rules.

Since the Woman, Life, Freedom movement, the enforcement of hijab restrictions in Iran has changed significantly. Although no formal legal reform has been enacted, the rules are no longer enforced in the same way as before.

While working with geospatial data of Montréal, the shape of the island on the map reminded me of a ponytail—like a gisoo. This association inspired the name of the project. I chose gisoo as a small tribute to the courage of the women in Iran who have fought for freedom and human rights.